-
[show abstract]
[hide abstract]
ABSTRACT: This study used organic thin-film gain media to study laser action in two-dimensional photonic crystals and quasi-crystals. The photonic crystal structures employed, although two-dimensional, do not possess a complete two-dimensional band-gap. A pulsed nitrogen laser with pulse width 2 ns and 337 nm light is used to photo-excite the structure. A CCD/spectrometer is used to measure the emission spectra. The PBD molecules absorb the pump and funnel the excitation to the DCM dye molecules through cascade Forster transfer. The gain medium can be approximated by a four-level system.
Lasers and Electro-Optics Society, 2004. LEOS 2004. The 17th Annual Meeting of the IEEE; 12/2004
-
[show abstract]
[hide abstract]
ABSTRACT: Single-mode planar waveguides were fabricated from chalcogenide glass compounds with large Kerr nonlinearities. Strong self-phase modulation of subpicosecond pulses along with low linear and nonlinear absorption losses demonstrates the potential for ultrafast, low-power, all-optical processing applications.
Optics Letters 04/2002; 27(5):363-5. · 3.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A set of high-intensity pulse propagation experiments in optical fibre gratings, leading to slow propagation and soliton formation,
is discussed. The results are analyzed using the nonlinear Schrödinger equation, which applies in almost the entire regime
we consider here. Indeed, good quantitative agreement between experiments and theory and numerical calculations is found,
except perhaps where second-order soliton dynamics is prominent.
12/2001: pages 57-70;
-
[show abstract]
[hide abstract]
ABSTRACT: Optical delay lines have some important applications, notably in
optical communication systems and in phased arrays. These devices are
based on the concept of optical group delay, which, in turn, can be
understood as the property of an optical filter. Optical filters are
well-understood devices and, in particular, their dispersive properties
determine the group delay response. We review these dispersive
properties and point out some of the inherent tradeoffs involved in
generating large group delay. Fiber Bragg gratings and recent results on
optical all-pass filters are used as examples
IEEE Journal of Quantum Electronics 05/2001; · 1.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We investigate the use of two-dimensional photonic crystal slabs to improve the directionality of output coupling from planar waveguides and distributed-feedback lasers. We present the theory underlying the operation of such structures and design criteria for emission in desired directions. As an example, we demonstrate a vertical coupler that is integrated with an organic distributed-feedback laser, use computer simulations to find its coupling constant and efficiency, and then discuss its feasibility.
Optics Letters 08/2000; 25(13):942-4. · 3.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Summary form only given. We propose a class of laser designs based on oneand two-dimensional (1D and 2D) photonic crystals (PCs), which result in surface emitting lasers with a fabrication process similar to that used in edge-emitting distributed feedback lasers. The basic principle employed in our designs is based on our recent discovery that the output coupling characteristics of 2D gratings (or PCs) are significantly different from 1D gratings. In 2D PCs, phase-matching conditions result in the coupling of light to one or a discrete number of directions instead of a cylindrical wave. We have designed numerous combinations of lasers and couplers, which have the potential to couple to a single spot normal to the plane of the waveguide. The lasers are experimentally realized with organic semiconductors.
Quantum Electronics and Laser Science Conference, 2000. (QELS 2000). Technical Digest; 06/2000
-
[show abstract]
[hide abstract]
ABSTRACT: Experiments demonstrate a dramatic decrease in polarization-instability threshold as an optical pulse is tuned near the short-wavelength edge of the photonic bandgap formed by a fiber Bragg grating. These enhanced nonlinear interactions and birefringent effects are modeled with coupled-mode numerical simulations. Nonlinearities are shown to increase much more rapidly than the effective birefringence as the pulse wavelength approaches the bandgap edge.
Optics Letters 06/2000; 25(10):749-51. · 3.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: High-speed optical communication requires ultrafast all-optical processing and switching capabilities. The Kerr nonlinearity, an ultrafast optical nonlinearity, is often used as the basic switching mechanism. A practical, small device that can be switched with ~1-pJ energies requires a large Kerr effect with minimal losses (both linear and nonlinear). We have investigated theoretically and experimentally a number of Se-based chalcogenide glasses. We have found a number of compounds with a Kerr nonlinearity hundreds of times larger than silica, making them excellent candidates for ultrafast all-optical devices.
Optics Letters 03/2000; 25(4):254-6. · 3.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A range of nonlinear effects have been predicted and observed experimentally in uniform optical fibers, where the typical interaction length for picosecond pulses is kilometers. Many of these effects have now been observed in one-dimensional photonic crystals, where dispersion is provided by a Bragg grating located in the core of an optical fiber, and the interaction length is reduced to only centimeters. This paper reviews nonlinear propagation of optical pulses in fiber Bragg gratings (FBGs). In particular, we show that propagation through a FBG enhances nonlinear interactions and demonstrate a dramatic decrease in polarization-instability threshold as an optical pulse is tuned near the photonic bandgap formed by the FBG
Lasers and Electro-Optics Society 2000 Annual Meeting. LEOS 2000. 13th Annual Meeting. IEEE; 02/2000
-
[show abstract]
[hide abstract]
ABSTRACT: Single-mode planar waveguides were fabricated from chalcogenide
glass compounds with large Kerr nonlinearities. Strong self-phase
modulation of sub-ps pulses along with low linear and nonlinear
absorption losses demonstrates the potential for integrated all-optical
switching applications
Optical Fiber Communication Conference, 2000; 02/2000
-
[show abstract]
[hide abstract]
ABSTRACT: We report on the far-field emission characteristics of two-dimensional photonic crystal-based organic waveguide lasers. The photonic crystals possess square vein, triangular, and honeycomb symmetries. The two-dimensional gratings are fabricated by employing soft lithographic methods. The far-field pattern that we observe is a result of out-of-plane diffractive coupling of the laser emission generated in the plane of the waveguide. This emission pattern offers a convenient and powerful way to evaluate the nature of laser action in such resonators. In devices which possess defects/breaks in the periodicity of the two-dimensional grating, laser emission generated in-plane is scattered in the plane of the waveguide. This phenomenon is the photonic crystal analogue of Kikuchi scattering in electronic crystals. © 1999 American Institute of Physics.
Journal of Applied Physics 11/1999; · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We conduct a comprehensive investigation of the lasing mechanism in a photonic crystal slab laser with a refractive index
that is periodic in two dimensions. Experimental spectra of laser structures fabricated with organic gain media are presented.
It is found that lasing frequencies can be explained in terms of Van Hove singularities in the density of modes. We also observe
lasing spectra that cannot be obtained from structures with one-dimensional periodicity, such as traditional distributed feedback
lasers. Lasing frequencies are computed using numerical techniques.
Applied Physics A 06/1999; 69(1):111-114. · 1.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We report an analysis of the operation of a new type of laser resonator with two-dimensional distributed feedback from a photonic crystal. The gain medium consists of a 2-(4-biphenylyl)-5(4-tert-butylphenyl)-1,3,4-oxadiazole host doped with Coumarin 490 and DCM and is deposited on lithographically patterned Si/SiO<sub>2</sub> structures. Bragg reflections caused by the grating diminish the group velocity of photons along some directions of crystallographic symmetry to zero, and the resulting feedback gives rise to laser oscillations. Dispersion relations for photons were calculated analytically and are used to interpret the laser emission spectra. 1999 American Institute of Physics.
Appl. Phys. Lett. 01/1999; 74:7-9.
-
[show abstract]
[hide abstract]
ABSTRACT: We demonstrate experimentally the compression of optical pulses, spectrally broadened by self-phase modulation occurring in the rod of a mode-locked Q-switched YLF laser, with an unchirped, apodized fiber Bragg grating in transmission. The compression is due to the strong dispersion of the Bragg grating at frequencies close to the edge of the photonic bandgap, in the passband, where the transmission is high. With the systems investigated, an 80-ps pulse, which is spectrally broadened, owing to self-phase modulation, with a peak nonlinear phase shift of D? = 7, is compressed to approximately 15 ps, in good agreement with theory and numerical simulations. The results demonstrate that photonic bandgap structures are promising devices for efficient pulse compression.
Applied Optics 11/1998; 37(30):7055-61. · 1.41 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Wavelength division multiplexing (WDM) communication systems
invariably require good optical filters meeting stringent requirements
on their amplitude response, the ideal being a perfectly rectangular
filter. To achieve high bandwidth utilization, the phase response of
these filters is of equal importance, with the ideal filter having
perfectly linear phase and therefore constant time delay and no
dispersion. This aspect of optical filters for WDM systems has not
received much attention until very recently. It is the objective of this
paper to consider the phase response and resulting dispersion of optical
filters in general and their impact on WDM system performance. To this
end we use general concepts from linear systems, in particular, minimum
and nonminimum phase response and the applicability of Hilbert
transforms (also known as Kramers-Kronig relations). We analyze three
different classes of optical filters, which are currently being used in
WDM systems and compare their performance in terms of their phase
response. Finally, we consider possible ways of linearizing the phase
response without affecting the amplitude response, in an attempt to
approximate the ideal filter and achieve the highest bandwidth
utilization
IEEE Journal of Quantum Electronics 09/1998; · 1.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Possibly the most appealing property of optical solitons is their
particle-like behavior. Solitons tend to survive perturbations and
collisions and interact nondestructively with each other. Indeed for
optical solitons which obey the integrable nonlinear Schrodinger
equation the interaction can be either attractive or repulsive,
depending on the relative phase of the two solitons. In both cases the
dynamics is well understood; either a periodic evolution (in the
attractive case) or for the repulsive case a two soliton solution which
is well approximated by the sum of the separated one soliton solutions.
Bragg solitons, on the other hand, are described by nonintegrable
equations. This means that, while they are also robust, in that they
possess a particle-like behavior, they show the distinct signature of
nonintegrability in that collisions are typically inelastic. In the
paper we report on experimental studies of interactions of Bragg
solitons in optical fibers
Quantum Electronics Conference, 1998. IQEC 98. Technical Digest. Summaries of papers presented at the International; 06/1998
-
[show abstract]
[hide abstract]
ABSTRACT: The authors report the fabrication and characteristics of organic
solid-state waveguide lasers with feedback from a photolithographically
defined rhomboid photonic bandgap lattice. The lattice is formed by
etching holes of depth 10-40 nm in SiO<sub>2</sub> and filling them with
the organic gain medium. The gain medium is part of a planar waveguide
formed by air/organic layer/SiO<sub>2</sub>. Normalised spontaneous
emission and amplified spontaneous emission (ASE) spectra are shown from
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) doped
with coumarin 490, DCMII and LDS821 dyes
Electronics Letters 02/1998; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Optically pumped lasers have been fabricated with
organic/polymeric materials capable of charge transport. The active
materials employed are doped films with small molecule hosts and dye,
oligomer, and conjugated polymer emitters. In these materials, the
excited states created in the host are transferred nonradiatively to the
guest molecules which are the emitters. This energy transfer results in
very low absorption losses at the emission wavelength and relatively
low-threshold powers for the onset of stimulated emission. Such gain
media have been successfully included in many types of resonators
including whispering-gallery mode, photonic bandgap, and distributed
Bragg reflector (DBR) based resonators. A number of novel patterning and
fabrication procedures have been developed for organic-based
lasers
IEEE Journal of Selected Topics in Quantum Electronics 02/1998; · 3.78 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Optically pumped laser emission has been observed from thin films of 8-hydroxyquinolinato aluminum (Alq) doped with a DCM dye deposited on a diffraction grating formed by imprinting a film of BCB with a mold. The BCB film, which is 4 μm thick, is deposited on a silicon or a flexible plastic substrate. Laser emission occurs at a wavelength near 655 nm which corresponds to the third order of the grating, which has a periodicity of ∼ 0.6 μm. © 1998 American Institute of Physics.
Applied Physics Letters 01/1998; 72(4):410-411. · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Summary form only given. We will report on the spatial and energetic funneling of excitations in organic films through one or more resonance energy transfer (or Forster transfer) steps which is shown to be promising in the design of materials for use in very low threshold lasers. The main advantages of employing gain media with Forster transfer in organic thin film lasers stem from a combination of efficient absorption of the pump light, very low absorption at the emission wavelength and broad tunability. The lowest threshold powers for stimulated emission (amplified spontaneous emission) in unpatterned films are less than 100 W/cm<sup>2</sup>. We also describe the characteristics of a variety of photopumped lasers with Forster gain media. The cavity designs we have employed include planar microdisks and oblate spheroids in which the lasing modes are whispering gallery modes, and distributed Bragg reflector based architectures. In many of these lasers, we have obtained true single mode operation, with resolution limited linewidths of 0.2 nm. The materials used for the acceptors (guests) include molecules, oligomers as well as conjugated polymers
Lasers and Electro-Optics Society Annual Meeting, 1997. LEOS '97 10th Annual Meeting. Conference Proceedings., IEEE; 12/1997
